linux-kernel - Re: [PATCH] clocksource: Store reg field within struct clocksource

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Message-ID: <564DC006.8000406@sigmadesigns.com>
Date:	Thu, 19 Nov 2015 13:26:46 +0100
From:	Marc Gonzalez <marc_gonzalez@...madesigns.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mans Rullgard <mans@...sr.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Nicolas Pitre <nico@...aro.org>,
	Tony Lindgren <tony@...mide.com>,
	Sebastian Frias <sebastian_frias@...madesigns.com>
Subject: Re: [PATCH] clocksource: Store reg field within struct clocksource

On 19/11/2015 12:14, Thomas Gleixner wrote:

> So yes, the alignment of the clocksource struct is not longer
> relevant. The case where we access clocksource->max_cycles is when
> CONFIG_DEBUG_TIMEKEEPING is enabled, which imposes worse performance
> problems to timekeeping than the extra cacheline.
> 
> So the simple solution for this issue is indeed the one liner below.

It would make sense to also remove the comment emphasizing the
alignment requirement.

Regards.

8<-------------------

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 278dd279a7a8..6a0f86a9a92d 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -64,10 +64,6 @@ struct module;
  * @owner:             module reference, must be set by clocksource in modules
  */
 struct clocksource {
-       /*
-        * Hotpath data, fits in a single cache line when the
-        * clocksource itself is cacheline aligned.
-        */
        cycle_t (*read)(struct clocksource *cs);
        cycle_t mask;
        u32 mult;
@@ -95,7 +91,7 @@ struct clocksource {
        cycle_t wd_last;
 #endif
        struct module *owner;
-} ____cacheline_aligned;
+};
 
 /*
  * Clock source flags bits::

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